All the notes of the chromatic scale are spaced at equal (‘symmetrical’) , semitone, intervals. This scale is therefore a called a symmetric scale. One can also form a symmetric scale by selecting notes spaced at whole tone (2 semitones) intervals. This scale consists of six notes only and is called the Whole-tone scale.

Here the C whole-tone scale.

Any of the above notes can form the tonic of the whole-tone scale using the same six notes.

Jazz improvisers were quick to take up this new sound for improvisation over augmented triads and augmented 7th chords (+7 or 7^aug).

8-note Symmetric scales

Other symmetric scales can be formed by alternating note spacings of tones and semitones. There are two possibilities.

8-note Dominant scale (semitone – tone – semitone – tone -)
This scale starts with a semitone between the tonic and 2nd note, then a tone between the 2nd and 3rd notes, again a semitone between the 3rd and 4th note, and so on.

In Jazz this scale is used as an alternative choice for improvisation over dominant 7th and altered dominant 7th chords .

8-note Diminished scale (tone – semitone – tone – semitone – )
This scale starts with a tone between the tonic and 2nd note, then a semitone between the 2nd and 3rd notes, again a tone between the 3rd and 4th note, and so on.

In Jazz this scale is used for improvisation over diminished chords